Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session JO7: Strongly Coupled Plasmas, Quantum Plasmas, and Numerical Techniques |
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Chair: Jerome Daligault, Los Alamos National Laboratory Room: Galerie 6 |
Tuesday, October 28, 2014 2:00PM - 2:12PM |
JO7.00001: A new class of strongly coupled plasmas inspired by sonoluminescence Alexander Bataller, Guillaume Plateau, Brian Kappus, Seth Putterman Sonoluminescence originates in a strongly coupled plasma with a near liquid density and a temperature of $\sim$10,000 K. This plasma is in LTE and therefore, it should be a general thermodynamic state. To test the universality of sonoluminescence, similar plasma conditions were generated using femtosecond laser breakdown in high pressure gases. Calibrated streak spectroscopy reveals both transport and thermodynamic properties of a strongly coupled plasma. A blackbody spectrum, which persists long after the exciting laser has turned off, indicates the presence of a highly ionized LTE microplasma. In parallel with sonoluminescence, this thermodynamic state is achieved via a considerable reduction in the ionization potential. [Preview Abstract] |
Tuesday, October 28, 2014 2:12PM - 2:24PM |
JO7.00002: Non-Markovian Collisional Dynamics in a Strongly Coupled Ultracold Neutral Plasma Trevor Strickler, Thomas Langin, Patrick McQuillen, Georg Bannasch, Thomas Pohl, Thomas Killian Collision rates in weakly coupled plasmas are well-described by the Landau-Spitzer formula; however, the formula breaks down for plasmas in the strongly coupled regime where collisions may be governed by non-Markovian dynamics. In this work, we present experimental results concerning non-Markovian processes in a strongly coupled ultracold neutral plasma (UCNP) created by photoionizing strontium atoms in a magneto-optical trap. Our diagnostic uses optical pumping to create spin ``tagged'' subpopulations of ions having skewed velocity distributions that then relax back to equilibrium. In previous work, we used this technique with LIF imaging to extract ion-ion collision rates of strongly coupled UCNPs. With newly improved time resolution (down to 30 ns), we have now explored the very early time dynamics of these skewed ion distributions within a few 100 ns after the optical pumping, where molecular dynamics simulations predict non-Markovian deviations from the exponential velocity damping expected for weakly coupled systems. We observe evidence of non-exponential damping and compare results across a range of plasma parameters. [Preview Abstract] |
Tuesday, October 28, 2014 2:24PM - 2:36PM |
JO7.00003: Ion Temperature Evolution in an Ultracold Neutral Plasma Patrick McQuillen, Trevor Strickler, Thomas Langin Ultracold neutral plasmas (UNPs), created by photoionizing laser-cooled atoms have ions which inherit very low temperatures. However, a process known as disorder induced heating (correlation heating) quickly heats the ions, limiting the equilibrium shielded ion Coulomb coupling parameter to approximately two, regardless of initial conditions. This places UNPs just within the strongly coupled (non-ideal) regime. Subsequently, competing cooling and heating mechanisms have been predicted to determine the ion temperature evolution. Using laser induced fluorescence spectroscopy and taking care to minimize extraneous heating processes like heating from ion-acoustic-wave excitations; we have measured the ion temperature evolution of UNPs, observing both adiabatic cooling of the ions, by up to an order of magnitude and collisional heating by the electrons. These measurements will be presented along with efforts to model the ion temperature evolution as well as discussion of the Coulomb coupling parameter. We gratefully acknowledge support from the Department of Energy and National Science Foundation (PHY-0714603) and the Air Force Office of Scientific Research (FA9550-12-1-0267). [Preview Abstract] |
Tuesday, October 28, 2014 2:36PM - 2:48PM |
JO7.00004: Linear Electrostatic Instabilities in a Quantum Plasma with Arbitrary Level of Degeneracy Shane Rightley, Dmitri Uzdensky In this study, a fully kinetic complex solution of the linear dispersion relation for electrostatic waves in a quantum electron plasma with arbitrarily-degenerate Fermi-Dirac equilibrium distribution is extended to cases with multiple drifting populations of electrons. Building on a previous numerical procedure, we allow for a full linear analysis of quantum kinetic effects in one-dimensional streaming instabilities. The bump-on-tail instability is analyzed for an arbitrarily degenerate electron background. Additional focus is on instabilities in systems with counter-streaming populations with varying degrees of degeneracy. These instabilities have been previously studied analytically in some simple cases. This presentation discusses specifically the kinetic effects on these instabilities, which are of well-known importance to classical plasmas. Additionally, our use of a physically realistic Fermi-Dirac distribution function is novel. The intent of the analysis is towards increasing the understanding of quantum plasma physics as a field and laying a foundation for further studies. [Preview Abstract] |
Tuesday, October 28, 2014 2:48PM - 3:00PM |
JO7.00005: Evidence of a new quantization constant in collisionless plasmas George Livadiotis Recent plasma analyses revealed strong evidence about the value and nature of the new quantization constant $\hbar_{\mathrm{\ast }}$, that is similar to the Planck constant $\hbar $, but 12 orders of magnitude larger. Planck's constant constitutes the phase-space quantum for individual and uncorrelated particles, while the new constant $\hbar $* describes the phase-space quantum for particle systems characterized by local correlations, such as collisionless plasmas. In plasmas, long-range interactions induce local correlations, manifested by the presence of a correlation length between particles. This divides the system into an ensemble of clusters of correlated particles. The particles within each of these ``correlation clusters'' participate altogether to this new type of quantization. Quantum mechanics requires the existence of a non-zero least action, the quantization constant, but do not provide its specific value. The new developments point toward a new quantum-mechanical approach that will be based on the new quantization constant. If true, plasmas can be studied in a new way, following the framework of quantum and statistical mechanics, but on a much larger scale. [Preview Abstract] |
Tuesday, October 28, 2014 3:00PM - 3:12PM |
JO7.00006: Fano-like resonances in strongly coupled binary Coulomb systems Luciano Silvestri, Gabor J. Kalman, Zolt\'an Donk\'o, Peter Hartmann, Hanno K\"{a}hlert Molecular Dynamics (MD) simulation of a strongly coupled binary ionic mixture has revealed the presence of a sharp minimum of several orders of magnitude in the dynamical density (current) fluctuation spectrum of the system. This phenomenon is reminiscent of the well-known Fano anti-resonance observed in various physical systems. The Fano resonance effect can be understood on the basis of a classical model as a feature of the response function of a multi-resonant system, and therefore it is a phenomenon that should occur in classical systems as well. What, however, is not widely recognized is that there must be a corollary to this phenomenon as demanded by the Fluctuation Dissipation Theorem: the equilibrium fluctuation spectrum of a strongly coupled system has to display a similar spectral feature. We present a theoretical description based on the Quasi Localized Charge Approximation, reformulated to include collisional effects, in order to explain the simulation results. The essence of the phenomenon is that the minimum is due to the interference between the two damped plasmon modes of a binary system. The validity of the theoretical model has been verified by further MD simulations and an excellent agreement between theory and observation has been demonstrated. [Preview Abstract] |
Tuesday, October 28, 2014 3:12PM - 3:24PM |
JO7.00007: ABSTRACT WITHDRAWN |
Tuesday, October 28, 2014 3:24PM - 3:36PM |
JO7.00008: Experimental determinations of the sound speed and the Gr\"{u}neisen coefficient of liquid Deuterium along the principal Hugoniot using a first order perturbation analysis Dayne Fratanduono, Peter Celliers, Damian Hicks, Tom Boehly, David Munro, Gilbert Collins Using a first order perturbation analysis, we have measured the sound speed and Gr\"{u}neisen coefficient of liquid Deuterium along the principal Hugoniot. Experiments were conducted at the OMEGA laser facility in which perturbations in the drive were measured at the shock front in both the transparent standard (Quartz) and liquid Deuterium sample. Since the EOS of the transparent standard is well known, a first order perturbation analysis enables extraction of the sound speed and Gr\"{u}neisen coefficient through the correlation of events on the shock front in both materials. These measurements, represent the first high-pressure (\textgreater 100 GPa) dynamic measurements of Deuterium EOS derivatives which will further advance EOS modeling capabilities important to astrophysics, planetary physics and ICF.This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Tuesday, October 28, 2014 3:36PM - 3:48PM |
JO7.00009: Introduction to a new computational method of electron-ion quantum plasmas of an arbitrary degeneracy In-Gee Kim, Michael Murillo A new computational approach for calculating the physical properties of quantum mechanical electron-ion plasmas of an arbitrary degeneracy in terms of the random-phase approximation is introduced. The numerical computation for the arbitrarily degenerated plasmas is achieved by employing the sinc quadrature rule for the corresponding improper integrals. Although the model system is assumed to be isotropic and homogeneous, the method provides high degrees of freedom for choosing the model interactions. We are able to investigate the possible elementary excitations, as well as instabilities, for the interacting quantum two-component system for the broad range of parameter space. [Preview Abstract] |
Tuesday, October 28, 2014 3:48PM - 4:00PM |
JO7.00010: Unusual stimulated Raman scattering in a plasma metamaterial Eduardo P. Alves, Ricardo Fonseca, Luis O. Silva Electromagnetic (e.m.) metamaterials using plasmas have recently been demonstrated to exhibit extraordinary e.m. features [Sakai, 2012]. We aim to exploit plasma nonlinearity combined with metamaterial structures to assess new and unexplored nonlinear e.m. phenomena. We have developed a unique numerical framework to study nonlinear plasma processes in the presence of a strong background magnetic permeability (e.g., background SRR metamaterial [Pendry, 1999]). We combine the particle-in-cell method, to describe the plasma dynamics self-consistently, with a dispersive-FDTD Maxwell solver to incorporate the effects of a strong background magnetic permeability [Taflove, 2000]. This framework allows us to investigate the extraordinary character of fundamental nonlinear plasma effects in the presence of a strong magnetic permeability, which is generally neglected in standard plasma physics. In this work, we explore stimulated Raman scattering (SRS) in a plasma metamaterial. We have generalized the SRS theory to incorporate the effect of an arbitrary background magnetic permeability. The generalized theory is in good agreement with our numerical framework and we demonstrate the unusual operation of SRS in a parameter window that is not accessible in a simple plasma medium. [Preview Abstract] |
Tuesday, October 28, 2014 4:00PM - 4:12PM |
JO7.00011: Exploration of LWFA Parameter Regimes Using Truncated Azimuthal Modal Geometry in the OSIRIS Simulation Framework Asher Davidson In plasma based accelerators (LWFA and PWFA), the methods of injecting high quality electron bunches into the accelerating wakefield is of utmost importance for various applications. Numerous particle-in-cell (PIC) simulations are conducted in order to study various methods of injection and the ideal parameters thereof. 2D slab-geometry simulations are computationally inexpensive, but they are quantitatively, and sometimes even qualitatively inaccurate. One method for reducing the computational load of a 3D simulation is by utilizing a truncated azimuthal mode expansion into the OSIRIS simulation framework [A. Lifschitz et. al 228 (5) (2009)]. Comparison with 3D LWFA simulations shows a great degree of consistency in the characteristics of the self-trapped beam. In addition, higher order cylindrical modes may capture effects such as beam hosing and asymmetric spot size modulation. With this highly efficient 2D-hybrid algorithm it is possible to simulate parameter regimes and scaling laws that are difficult to do in a full 3D Cartesian simulation. Relativistic spot-size self-focusing, which cannot be accurately described in a 2D slab geometry, is also studied. [Preview Abstract] |
Tuesday, October 28, 2014 4:12PM - 4:24PM |
JO7.00012: A finite mass based method for Vlasov-Poisson simulations David Larson, Christopher Young A method for the numerical simulation of plasma dynamics using discrete particles is introduced. The shape function kinetics (SFK) method is based on decomposing the mass into discrete particles using shape functions of compact support. The particle positions and shape evolve in response to internal velocity spread and external forces. Remapping is necessary in order to maintain accuracy and two strategies for remapping the particles are discussed. Numerical simulations of standard test problems illustrate the advantages of the method which include very low noise compared to the standard particle-in-cell technique, inherent positivity, large dynamic range, and ease of implementation. [Preview Abstract] |
Tuesday, October 28, 2014 4:24PM - 4:36PM |
JO7.00013: An Electromagnetic Particle-In-Cell Framework with Cut-Cells and Unstructured Mesh Regions Collin Meierbachtol, Andrew Greenwood, John Verboncoeur, Andrew Christlieb Many electromagnetic particle-in-cell (EM-PIC) simulations are solved on Cartesian meshes, where curved or slanted metallic boundaries are approximated via staircasing. As a result, numerical errors are introduced in both the field and particle behaviors. Cut-cells inserted near these irregular metallic boundaries can eliminate staircasing, but have difficulty in resolving small geometric features. Unstructured meshes can successfully resolve irregular boundaries and small features via local mesh refinement, but can also increase simulation run time. In order to achieve good geometric representation while minimally increasing the simulation run time, we propose a hybrid mesh EM-PIC framework. The simulation domain is mostly filled with a Cartesian mesh. Slanted or large radius metallic boundaries are represented via cut-cells, while the mesh surrounding any small physical features is unstructured. Electromagnetic fields are updated via explicit finite difference methods in both the Cartesian and cut-cells, and finite element methods within any unstructured mesh regions. Particle positions are updated and tracked throughout the hybrid mesh. [Preview Abstract] |
Tuesday, October 28, 2014 4:36PM - 4:48PM |
JO7.00014: A Geometrical Version of the Maxwell-Vlasov Hamiltonian Structure Michel Vittot, Philip Morrison We present a geometrization of the Hamiltonian approach of classical electrodynamics, via (non-canonical) Poisson structures. This relativistic Hamiltonian framework (introduced by Morrison, Marsden, Weinstein) is a field theory written in terms of differential forms, independently of the gauge potentials. This algebraic and geometric description of the Vlasov kinetics is well suited for a perturbation theory, in a strong inhomogeneous magnetic field (expansion in 1/B, with all the curvature terms...), like in magnetically confined plasmas, and in any coordinates, for instance adapted to a Tokamak (toroidal coordinates, or else...). [Preview Abstract] |
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